A syringe of the above type can be used in a variety of fields, for instance as sampling or injection syringe in the medical field.
An application which in this case is particularly preferred but not limiting is, for instance, in the pharmaceutical and biotechnology field and to some extent also in fields such as foods and cosmetics. In these fields there is a need for routine sampling and analysis of different media, for instance for microbiological control, cell counting or, where appropriate, chemical analyses, or supply of regulating or active media in certain process steps in manufacture of products in the fields in question.
In such manufacture involving stringent requirements as to no contamination, or minor contamination, of the media included in the process, manufacture normally takes place in a closed process vessel. There is, however, a risk of contamination when one or more media are to be supplied to the process vessel or a sample is to be taken from the process vessel. Due to this risk of contamination in and around the process vessel, the supply and sampling of the media therefore take place in clean room environment, which requires great investments, expensive equipment and acceptable working conditions for the staff.
The syringe according to the present invention is in the first place, but not exclusively, intended to be used in contamination-free take-up from a process vessel to a collecting vessel or the like. The syringe can be used to transfer fluid from a collecting vessel and supply the fluid to a process vessel or vice versa. The syringe can also be arranged for other dosing, transport or sampling, such as transfer of the fluid to a laboratory for analysis etc.
In sampling according to prior-art technique, there are problems with false positive results, that is that the medium from which samples are taken is not contaminated but the sample nevertheless indicates contamination. This is a costly problem since the medium that is being sampled is often expensive and occurs in large volumes. False positive results are often due to problems with the sampling equipment which may cause contamination of the sample.
In prior-art syringes it has been found that the piston portion, in spite of its sealing engagement with the inside of the cylinder by means of a seal, in the form of at least one, but usually two sealing rings/flanges, by definition is not perfectly sealed against the inside of the cylinder.
When the piston portion initially, by the operating means, is moved upwards in the cylinder from a lower starting position to an upper “turning position” to take up/suck in medium from a collecting vessel, microorganisms and other very small contaminants, which after breaking of the sterile package or in some other manner get stuck on the syringe and then also on the inside of the cylinder, can pass the seal and enter the space on the fluid side of the piston portion where the contaminants mix with the sucked-in medium and contaminate it.
When the piston portion then, by the operating means, which can be a piston rod, is again moved inwards in the cylinder from the turning position to the starting position to discharge the medium to be added, analysed etc, the contaminants accompany the medium out of the syringe. This can wholly or partly destroy or damage the medium and make it difficult, or impossible, for the medium to be used, analysed etc. Owing to the contamination, the medium can alternately, or in addition, be dangerous to use.
It has also been found that as the piston portion moves inwards in the cylinder there easily forms, despite the seal, a very thin film of the received medium on the inside of the cylinder, that is on the piston portion side opposite to the fluid side. If the medium has a strong odour, the user clearly notices this around the syringe. If the medium is injurious to health or dangerous to the environment or even poisonous, the forming of film may constitute a serious health or environmental hazard. Furthermore this film can additionally increase the risk that contaminants get stuck on the inside of the cylinder, and in the cases where the syringe is used several times before being finally discarded or cleaned for reuse, the risk also increases that the medium in the syringe should be contaminated by contaminants or microorganisms more easily getting stuck on the film formed.
An additional risk of prior-art syringes is that the contamination guard, for instance the protective bellows, is positioned so that it risks being damaged in the handling of the syringe. If a hole occurs in the contamination guard, there is a risk that contaminants enter the syringe and contaminate the medium in the cylinder of the syringe.